The present disclosure relates to a semiconductor device and its memory access control method. For example, the present disclosure relates to a semiconductor device including a main-arithmetic unit that executes a program, a sub-arithmetic unit that executes a process of a part of the program, and a shared memory that is shared by the main-arithmetic unit and the sub-arithmetic unit, and relates to its memory access control method.
In a semiconductor device that performs various processes based on a program, there are cases where a plurality of programs are executed in one semiconductor device. Such a semiconductor device requires a memory protection mechanism to prevent interference in a memory space used by a plurality of programs (e.g., to prevent a plurality of programs from using the same area in a memory space). Therefore, Japanese Unexamined Patent Application Publication No. 2014-48849 discloses an example of the memory protection mechanism.
A semiconductor device disclosed in Japanese Unexamined Patent Application Publication No. 2014-48849 is a safety control system in which a drive control unit that performs drive control of a device to be controlled and a safety control unit that performs safety control related to the drive control are disposed in one processor, and in which: a predetermined storage area is allocated as a data storage area for each of the drive control unit and the safety control unit in advance; and the safety control system includes memory protection information storage means in which the storage area allocated to the safety control unit is registered as a storage area that cannot be accessed by the drive control unit, and memory protection means for, when the drive control unit performs memory access, referring to the access destination and registration information registered in the memory protection information storage means, and when the access destination is in the storage area that cannot be accessed by the drive control unit, preventing the drive control unit from accessing the storage area allocated to the safety control unit.